Open sites can be readily colonised by a new weed species, so the planting of native trees, shrubs and grasses, as well as mulching the weeded area, will make a big difference in reducing weed re-growth.
In coastal areas, you may find it worthwhile to protect native plants from wind and salt spray while they become established. You can also encourage your native plants to grow more quickly by weeding around your plantings to reduce the competition from weeds. Be careful not to dig deeply around desirable plants so you don't damage their roots.
Weeds can be reduced or suppressed by adding a layer of mulch around each plant. Most rotted organic matter such as leaf mould, compost, straw, lawn clippings or silage can be used for mulching. Old wool carpet or underlay provides a degradable weed mat.
Remember, a new plant needs water - it is not enough to just plant it.